This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Loop motions play a critical role in the catalytic mechanism of the Yersinia protein tyrosine phosphatase, YopH. The goal of this project is to characterize loop motion in YopH using NMR relaxation dispersion experiments.